In German Patent No. 2,627,880, there is described a nozzle design for forming atomized sprays in which a gas medium and a liquid medium are combined in a mixing chamber and then expelled from the nozzle as atomized liquid or as tiny gas bubbles, depending on the relative proportions of the liquid and gas. The atomization results from a considerable drop in pressure as the two-phase mixture leaves the nozzle. The nozzle is based on the principle that a properly-formed two-phase mixture has an effective sonic velocity that is less than the sonic velocity of either the gas stream alone or liquid stream alone, estimated to be as low as 10 percent of the sonic velocity of water. This nozzle design has many attributes, including lower pressures, lower pressure drop, reduced velocities, reduced air consumption and reduced orifice abrasion.
However, the nozzle consists of a single orifice which has many shortcomings. For example, if a large duct is to be completely filled with fine liquid spray, the 12.degree. to 15.degree. spray angle generated by the single orifice may require placement of the nozzle many meters back in the duct or the use of a multiple number of individual nozzles to achieve the objective.
In the nozzle design described in the above-noted German Patent, the liquid feed is effected through the same pipe as the spray is ejected from, while the gas is fed from the side to a chamber which surrounds and communicates with the liquid feed through a plurality of openings in the liquid feed pipe just upstream of the orifice, so as to form the two-phase mixture. This feed arrangement often is unsuitable for the feed lines available and the intended end use.